1. Field of the Invention
The present invention generally relates to steam generator maintenance tooling such as sludge removal systems and more particularly to such systems for use in the stay dome area on the secondary side of the steam generator.
2. Description of the Prior Art
Buildup of sediment or sludge on the secondary face of the tube sheet in a boiler or steam generator has been proven to contribute to degradation of the tube material. It is a common practice to lance the tube sheet and tube support plates with high pressure water to wash the sludge from between the tubes to a suction pickup where it can be removed from the steam generator. Most re-circulating steam generators have a wide lane that separates the hot leg tubes from the cold leg tubes. A wand that contains high pressure nozzles is usually inserted into this lane and the sludge forced out to the area between the steam generator shell and the tube bundle, called the annulus. From the annulus the sludge is easily washed to a suction pickup and removed from the steam generator.
In some re-circulating steam generators the geometry of the tube bundle does not permit lancing to be efficiently performed from a lane in the tube bundle. These generators must be lanced either totally or partially from the annulus. When lanced from the annulus, suction pickup and alignment of the annulus-based device with the suction pickup must be done from the wide tube-free lane that separates the hot leg tubes from the cold leg tubes. Additionally, some steam generators contain a circular cutout of tubes in the center of the tube bundle. The center of this tube cutout may contain a spherical dome, known as a stay dome, which must be negotiated by tooling in order to provide suction pickup and deliver alignment platforms allowing annulus lancing to be most effective.